First thing I would do is get it out of my head to be shooting at game 6 and 7 hundred yards to start. I would back down to more resonable ranges like 3 to 4 hundred after I was able to shoot 200 with consistency.
Get a set of good rings and a scope, I'm not a scope snob so I will not tell you what I think is the best brand.
Then find a place where you can practice 3 and 4 hundred yard shooting, even that distance is hard to find in my area to practic distance shooting. We can get 200 fairly easy but any longer is really really hard.
I own beach frontage 6.5 hours from home and can get that range practice there but not often.
Al